The convergence of information from different sensory modalities upon single neurons has been demonstrated in several regions of the brain. However, little is known about the interaction of these inputs or the functional purpose of converging sensory input upon the same cell. This project proposes to study the manner in which neurons in the cat superior colliculus respond to stimuli from more than one sensory modality. Cells in the cat superior colliculus have been chosen for study because of the large volume of existing informaton regarding the organization and functional role of multiple sensory inputs here, and the response properties of its cells to unimodal sensory stimulation. Single unit responses to controlled visual, tactile, and auditory stimuli will be recorded extracellularly with tungsten microelectrodes. Stimuli will be presented individually and together, and at various preprogrammed intervals. Attempts will be made to evaluate possible excitatory and/or inhibitory interactions as well as to determine the incidence and distribution of multimodal neurons. These experiments represent a first step in the evaluation of the functional role of multimodal convergence in the superior colliculus and should be of significant value in understanding the contribution of sensory convergence on single neurons in all parts of the nervous system.